Projection screen

ABSTRACT

A projection screen comprises a flexible covering forming the picture projecting surface which is stretched to a planar form by an inflatable stiffening structure of flexible material enclosed by the covering.

0 United States Patent [1 1 [i 3,720,455 Sahlin 1March 13, 1973PROJECTION SCREEN 717,034 2 1942 Germany ..350/117 Inventor: John CarlErik Sahlin, sergels g 448,823 8/1927 Germany ..350/ll7 5-217 57 SwedenPrimary Examiner-Samuel S. Matthews [22] Filed: Aug. 2, 1971 AssistantExaminer-Richard M. Sheer pp No: 168,027 AttorneyLerner, David &Littenberg [57] ABSTRACT [52] US. Cl ..350/ll7 A pro ection screencomprises a flexible coverlng [5 1] Int. Cl. ..G03b 21/56 forming thepicture projecting Surface which is [58] FIG! of Search ..350/1 17;40/155 Stretched to a planar form by an inflatable stiffening structureof flexible material enclosed by the covering. [56] References Cited 5Claims, 4 Drawing Figures FOREIGN PATENTS OR APPLICATIONS 805,21612/1958 Great Britain ..3SO/l l7 :7 II I r l I I i l I l I l 4/ I l l I1 l l l I l 1' PROJECTION SCREEN The present invention relates to aprojection screen having a plane picture projection surface.

An object of the invention is to provide a projection screen which maybe easily transported and stored in a rolled or folded state and has alow weight in order to facilitate transport as well as suspension orraising of the screen.

According to the invention there is provided a projection screen forminga picture projection surface comprising a covering of flexible material,an inflatable flexible tube arranged inside the covering to form a frametherein, and an inflatable stiffening member of flexible materialarranged inside the frame, the frame and the stiffening member whenbeing inflated will stretch and rigidify the covering forming thepicture projection surface of the screen.

The invention will now be described in detail with reference to thedrawing showing illustrative embodiments of the invention.

FIG. 1 is an elevational view, partly in section, of one embodiment ofthe projection screen according to the invention;

FIG. 2 is an enlarged cross sectional view taken along the line II II inFIG. 1;

FIG. 3 is a cross sectional view in accordance with FIG. 2 of a modifiedembodiment;

FIG. 4 is a view in accordance with FIG. 1 of another embodiment of theprojection screen according to the invention.

The projection screen is as a whole made of flexible material such ascoated fabric and comprises an outer square covering which is closed orclosable along the four margins thereof and resembles a conventionalcushion-cover. One or both of the faces of the covering may be coatedexternally with a light-reflecting material. Inside the covering thereis provided a stiffening structure including a frame 11 formed by aninflatable tube, and a stiffening member formed as a circular ring.

12 also formed by an inflatable tube and inscribed into the frame. Thering is of a smaller dimension in the transverse direction of the screenthan the frame 11 as will be seen from FIG. 2, and is connected, e.g.,welded to the frame in the four points of tangency. For the inflation ofthe frame there are provided two diametrically opposed valves 13 whilethe ring 12 is separately inflatable through a small hose 14 whichextends from the covering beyond the frame at a suitable location and isprovided with a valve or other closure member. The stiffening structureformed by the frame and the ring is connected with the covering only atthe locations where the valves 13 extend from the covering. For the restthe stiffening structure is loosely arranged inside the covering. Whenthe stiffening structure is being inflated, the frame will fill out themarginal portions of the covering and will stretch the covering therebytaking out folds and wrinkles, if any, provided that the circumferenceof the inflated frame intentionally has been made as large as orsomewhat larger than the circumference of the covering. Due to the factthat the stiffening structure is arranged loosely inside the covering itwill adapt itself to the available space and will fill out such spacewithout causing folding or distortion of the covering. Thus, thecovering will form a plane picture projection surface. It should benoted that the covering l0 proper will not be inflated, only thestiffening structure thereof. In the covering wall there should beprovided small openings to allow pressure equalization between theinterior of the covering and the surrounding atmosphere. When thestiffening structure is being inflated the frame will be applied againstthe inner surface of the covering, forming right angles at the fourcorners thereof although the frame is not necessarily prefabricated withright angles corners. The ring functions as an arc supporting the foursides of the frame in order to eliminate a tendency thereof to sag inthe central portions thereof.

When the stiffening structure is not inflated the pro- 15 jection screenmay be rolled or folded to a small lowweight package which is easy totransport and store. When the screen is to be used the stiffeningstructure will be inflated in order to stretch the covering 10. Thereby,the screen will be sufficiently rigid to be placed on a support orleaned against a wall without collapsing. Furthermore, the screen may besuspended or raised by the valves 13 or by one or more flaps which maybe provided at the top margin of the covering 10, by using simpler andless bulky means than those required in connection with the handling ofconventional projection screens. Since the screen has a low weight itmay easily be inclined forwardly in order to counteract parallax.

In the modified embodiment according to FIG. 3 the flexible tube 11 isreplaced by two identical tubes 11A and 11B interconnected as by weldingin side by side relationship. The ring 12 is arranged in the innergroove formed between the two tubes 11A and 11B and, thereby, the ringis maintained in a proper position within the inflated frame formed bythe tubes 11A and 11B without the necessity to arrange aninterconnection between these tubes and the ring.

In the embodiment according to FIG. 4 there is provided as a substitutefor the ring 12 in the embodiment described above a grid 15 which isinflatable separately and is connected with the frame 11 at the innermargin thereof. This grid has a smaller dimension in the transversedirection of the screen than the frame 1 l as in the embodimentsaccording to FIGS. 1 to 3.

The part of the stiffening structure arranged inwardly of the frame,i.e., the ring 12 and the grid 15, respectively, should have a smallerdimension in the transverse direction of the screen than the frame andshould be centered in relation thereto in order not to form bulges inthe faces of the covering. There are no requirements as far as theappearance of the stiffening structure is concerned since this structurewill be concealed by the covering. Since this structure is notnecessarily welded to the covering the latter may have one face ofprojection screen material and one face of elastic material allowing thecovering to yield when being stretched due to the inflation of thestiffening structure which may be formed of a material particularlysuitable therefor such as plastic foil or coated fabric or otherflexible material.

What I claim is:

l. A projection screen forming a picture projection surface comprising acovering of flexible material for forming a picture projection surfaceand having a front face and a back face, spaced from each other;

an inflatable flexible tube arranged in the space between the front andback faces of the covering to form a frame therein; and an inflatablestiffening member of flexible material arranged in the space between thefront and back faces of the covering of flexible material and within thebounds of the frame, the frame and the stiffening member when inflatedstretching and rigidifying the covering forming the picture projectionsurface of the screen. 2. A projection screen as claimed in claim 1wherein the stiffening member has a smaller dimension than the frame inthe transverse direction of the screen.

the stifiening member forms a grid surrounded by the frame.

5. A projection screen as claimed in claim 1 wherein the frame is formedby two inflatable tubes of flexible material interconnected in side byside relationship, the

stiffening member being received by a groove formed between the tubes.

1. A projection screen forming a picture projection surface comprising acovering of flexible material for forming a picture projection surfaceand having a front face and a back face, spaced from each other; aninflatable flexible tube arranged in the space between the front andback faces of the covering to form a frame therein; and an inflatablestiffening member of flexible material arranged in the space between thefront and back faces of the covering of flexible material and within thebounds of the frame, the frame and the stiffening member when inflatedstretching and rigidifying the covering forming the picture projectionsurface of the screen.
 1. A projection screen forming a pictureprojection surface comprising a covering of flexible material forforming a picture projection surface and having a front face and a backface, spaced from each other; an inflatable flexible tube arranged inthe space between the front and back faces of the covering to form aframe therein; and an inflatable stiffening member of flexible materialarranged in the space between the front and back faces of the coveringof flexible material and within the bounds of the frame, the frame andthe stiffening member when inflated stretching and rigidifying thecovering forming the picture projection surface of the screen.
 2. Aprojection screen as claimed in claim 1 wherein the stiffening memberhas a smaller dimension than the frame in the transverse direction ofthe screen.
 3. A projection screen as claimed in claim 1 wherein thestiffening member forms a ring inscribed in the frame.
 4. A projectionscreen as claimed in claim 1 wherein the stiffening member forms a gridsurrounded by the frame.